The field of the invention is motor controls for use in industrial applications, and in particular, motor controls which are operated from one or more remotely located pushbutton stations.
Industrial motor controls typically include a line contactor which is energized by a control circuit to close a set of contacts which apply power to the motor. The control circuit may be complex or relatively simple, but in almost all instances it includes a start switch which is connected to deliver power to the line contactor and a stop switch which interrupts that power. These switches are usually in the form of pushbutton switches in industrial applications.
In some industrial applications the start and stop pushbuttons may be located at stations which are located remotely from the motor and its control circuit. For example, the pushbutton station may be part of a centrally located control panel. In addition, more than one pushbutton station may be required where the motor is to be operated from more than one site.
In some industrial applications it is desirable to electrically isolate equipment. In chemical plants and refineries, for example, numerous motor controls are employed along with other electrical equipment to form a control system. If lightning were to strike part of this control system, it is desirable to limit the extent of the damage as much as possible. This may be accomplished by connecting the elements of the control system together using fiber optics rather than electrically conductive wire.